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/************************************************************************
 * © 2020-2023 SAP SE or an SAP affiliate company. All rights reserved. *
 ************************************************************************/
package com.sap.cds.jdbc.generic;

import static java.util.stream.Collectors.joining;

import java.text.MessageFormat;
import java.util.List;
import java.util.Locale;

import com.sap.cds.impl.parser.builder.ExpressionBuilder;
import com.sap.cds.impl.parser.token.CqnPlainImpl;
import com.sap.cds.jdbc.spi.FunctionMapper;
import com.sap.cds.ql.CQL;
import com.sap.cds.ql.Predicate;
import com.sap.cds.ql.cqn.CqnPlain;
import com.sap.cds.ql.cqn.CqnValue;

public class GenericFunctionMapper implements FunctionMapper {

	private static final String TOLOWER = "tolower";
	protected static final CqnPlain LIKE = CqnPlainImpl.plain("LIKE");
	protected static final CqnPlain ILIKE = CqnPlainImpl.plain("ILIKE");
	protected static final CqnPlain ESCAPE = CqnPlainImpl.plain("ESCAPE");

	@Override
	public String toSql(String cqnFunc, List args) {
		String func = cqnFunc.toLowerCase(Locale.US);
		switch (func) { // NOSONAR
		case "countdistinct":
			return "COUNT(DISTINCT " + args.get(0) + ")";
		case TOLOWER:
			return genericFuncToSql("LOWER", args);
		case "toupper":
			return genericFuncToSql("UPPER", args);
		case "current_date":
			return "current_date";
		case "current_time":
			return "current_time";
		case "current_timestamp":
			return "current_timestamp";
		case "singlevalue":
			String col = args.get(0);
			return MessageFormat.format("(case when min({0}) = max({0}) then min ({0}) end)", col);
		case "count":
			if (args.isEmpty()) {
				return "COUNT(*)";
			}
			break;
		case "matchespattern":
			return genericFuncToSql("LIKE_REGEX", args);
		}
		return genericFuncToSql(cqnFunc, args);
	}

	protected String genericFuncToSql(String func, List args) {
		return func.toUpperCase(Locale.US) + args.stream().collect(joining(", ", "(", ")"));
	}

	@Override
	public Predicate like(CqnValue value, CqnValue pattern, String esc, boolean caseInsensitive) {
		if (caseInsensitive) {
			value = CQL.func(TOLOWER, value);
			pattern = CQL.func(TOLOWER, pattern);
		}

		return ExpressionBuilder.create(value, LIKE, pattern, ESCAPE, CQL.constant(esc)).predicate();
	}

	protected Predicate ilike(CqnValue value, CqnValue pattern, String esc, boolean caseInsensitive) {
		CqnPlain operator = caseInsensitive ? ILIKE : LIKE;
		return ExpressionBuilder.create(value, operator, pattern, ESCAPE, CQL.constant(esc)).predicate();
	}
}